Vortex oil-water separator system providing clean water

ABSTRACT

A vortex separator is used to separate a mixture of materials of different densities, such as an oil-water mixture, into two components. The mixture is injected tangentially into one end of a cylindrical chamber at a high flow rate to impart a swirl to the flow in the chamber. Clean or recirculated water is injected into the chamber from the opposite end wall. The separated water is exhausted from the chamber through a port in the center of the end wall containing the water injectors, and the separated oil is exhausted through a small duct located at the center of the water exhaust port. Two or more separators may be connected in series for applications in which a ship&#39;&#39;s ballast or bilge water is separated into a first component containing primarily oil which can be stored in a small volume, and a second component of substantially pure water which may be dumped overboard. A baffle plate may be added in the chamber to improve the separation process.

United States Patent [191 Mesing [4 Dec. 25, 1973 VORTEX OIL-WATERSEPARATOR SYSTEM PROVIDING CLEAN WATER [75] inventor: Arthur E. Mesing,East Hartford,

Conn.

[73] Assignee: United Aircraft Corporation, East Hartford, Conn.

[22] Filed: Mar. 1, 1972 [21] Appl. No.: 230,665

[5 6] References Cited UNITED STATES PATENTS 12/1969 Willis et al2l0/5l2 X 6/l970 Minegishi 210/512 X 3,052,36l 9/1962 Whatley et al2l0/5l2 X 3,507,397 4/1970 Robinson 210/512 FORElGN PATENTS 0RAPPLICATIONS 996,826 l2/l95l France 210/521 3,48l,ll8 3,517,814

Primary Examiner-Samih N. Zaharna Assistant Examiner-F. F. CalvettiAtt0mey-Donald F. Bradley 57 ABSTRACT A vortex separator is used toseparate a mixture of materials of different densities, such as anoil-water mixture, into two components. The mixture is injectedtangentially into one end of a cylindrical chamber at a high flow rateto impart a swirl to the flow in the chamber. Clean or recirculatedwater is injected into the chamber from the opposite end wall. Theseparated water is exhausted from the chamber through a port in thecenter of the end wall containing the water injectors, and the separatedoil is exhausted through a small duct located at the-center of the waterexhaust port. Two or more separators may be connected in series forapplications in which a ships ballast or bilge water is separated into afirst component containing primarily oil which can be stored in a smallvolume, and a second component of substantially pure water which may bedumped overboard. A baffle plate may be added in the chamber to improvethe separation process.

7 Claims, 5 Drawing Figures PAIENTEB DEC 2 5197;

SNEEI 2 UP 3 VORTEX OIL-WATER SEPARATOR SYSTEM PROVIDING CLEAN WATERCROSS-REFERENCES TO RELATED APPLICATIONS This application containssubject matter related to the following two applications assigned to thesame assignee:

1. Application Ser. No. 230,663, filed Mar. 1, 1972 for Vortex Oil-WaterSeparator System Providing Clean Water in the name of David P. Millerand 2. Application Ser. No. 230,664, now abandoned,

filed Mar. 1, 1972 for Vortex Oil-Water Separator SystemProvidingCleanWater in the names of Arthur E. Mensing, Richard C. Stoeffler andJerome F. Jaminet.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to .a vortex separator for separating a mixture of two or morematerials of different densities into two separate components. Inparticular, this invention provides an improved separator for immiscibleliquids such as oil and water, and results in a component containingprimarily oil and a component of substantially pure water. A specificapplication of the invention is for separating ships ballast or bilgewater into an oil component which may be stored in a limited volume, anda water component which may be dumped overboard without contaminatingthe ocean water. The separator may be used for other applications suchas separating the liquid waste from restaurants or other businessestablishments into components, for example grease and water, for easeof disposal.

2. Description of the Prior Art Vortex separators for separating amixture of materials, either solid, liquid or gaseous, into twocomponents, are well known in the art. US. Pat. No. 3,566,610 uses acylindrical chamber into which a mixture such as an automobile exhaustis injected tangentially and a vortex generated to separate the mixtureinto two separate effluent streams of different densities. Copending US.patent application Ser. No. 125,232, now abandoned entitled Vortex FlowSystem for Separating Oil From an Oil-Water Mixture, and copendingapplication Ser. No. 125,154, now US. Pat. No. 3,743,102, entitled AVortex Separator Using Core Plates, both applications being filed Mar.17, 1971 and assigned to the same assignee as this application, discloseand claim a vortex separator in which a fluid mixture such as oil andwater is injected tangentially into a cylindrical chamber adjacent oneend thereof and a vortex generated so that the oil forms a core regionalong the axis of the chamber. The oil is removed from the chamberthrough a port located in the chamber end wall at the end of the chamberat which the mixture is injected, while the water is removed from a portin the center of the opposite end wall. A core plate may be providedcoaxially with the water exhaust port to assist in the formation of thecore of oil and prevent the oil from being removed with the water. Inanother configuration, a duct is provided in the center of the coreplatethrough which oil is removed from the chamber. A portion of theexhausted water may be recircu' lated through the chamber to assure thatonly relatively clean water is removed from the vortex separator.

In the above-identified copending applications, the main object is toassure that the oil removed from the vortex separator is relatively pureso that the oil may be stored in a limited volume. The intended use ofthe vortcx separators disclosed in the copending applications is toassist in the cleaning of oil spills on a body of water, to remove theoil from the water and to store it in a storage container until it maybe properly disposed of. If the water exhausted from the separatorcontains a substantial percentage of oil, it may be recirculated backthrough the separator, or dumped back into the body of water where itmay be recollected and passed again through the separator. If, however,a substantial amount of water were to be mixed with the oil removed fromthe separator, a much larger storage volume for the oil would berequired. The need for a large storage volume could severely inhibit theclean-up operation.

The present invention operates on the same general principles as thevortex separator disclosed in the prior art copending applications, butcontains modifications to the structure and operation of the vortexseparator in order to assure that the exhausted water is relativelyoil-free. One of the primary applications of the present invention is toclean the ballast or bilge tanks of ships to provide relatively purewater which can then be dumped overboard without contaminating the oceanor inland waters. If some water remains in the oil removed from theseparator, it is of little consequence since the amount of oil to bestored is relatively small.

SUMMARY OF THE INVENTION In accordance with the present invention, thereis provided an improved oil-water separator wherein an oil-water mixtureis injected tangentially into a circumferential chamber and a vortex isgenerated within the chamber forcing the lighter oil to form a corealong the axis of the chamber. The oil is removed from the chamberthrough a duct in the center of the end wall of the chamber opposite theend at which the oil-water mixture is injected. The water whichsurrounds the oil core is removed from the chamber through a port in thesame end wall in which the oil duct is located, the water removal portbeing concentric with and of larger radius than the oil removal duct.

In accordance with another aspect of the present invention, clean orrecirculated water is injected in a tangential direction into thecircumferential chamber adjacent the end wall from which the oil andwater are removed from the chamber. The addition of clean orrecirculated water assists in maintaining the vortex in the chamber, andresults in improved operation.

In accordance with a further aspect of the present invention, an annularbaffle plate having a circular aperture in the center thereof may beinserted in the vortex chamber parallel to the end walls and locatedbetween the end walls. its function is to reduce the number of small oilparticles which reach the end wall and may be exhausted with the water.

In accordance with another aspect of the present invention, two or morevortex separators may be connected in series if the water exhausted fromthe first vortex separator contains an undesirably high oil content sothat the remaining oil may be fully removed before the water is dumpedback into the ocean. If minimum oil storage volume is desired, thevortex separator of the type disclosed in the previously referencedcopending applications may be connected in series with a vortexseparator as disclosed herein, the first vortex separator of the seriesproducing relatively clean water which may be dumped into the ocean, andthe second vortex separator being fed the oil output from the firstseparator to produce substantially pure oil. The water output from thesecond separator may then be recirculated back into the first separatorto remove any oil contained in the water from the second vortexseparator.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a section of a preferredvortex separator of this invention.

FIG. 2 is a section of the vortex separator shown at 22 of FIG. 1.

FIG. 3 is a schematic of the vortex oil-water separator configurationshowing recirculation of a portion of the water exhausted from theseparator, and the addition of a baffle plate.

FIG. 4 is a schematic diagram of a system in which two staged separatorsare used for cleaning ballast water.

FIG. 5 is a schematic diagram of an additional system for cleaningballast water.

DESCRIPTION OF THE PREFERRED EMBODIMENT Oil pollution on shipping lanesand in harbors is a recurring and increasing problem. A majorcontributor to this pollution is the oil contained in large volumes ofballast water that are discharged from tankers. Detection of these lowlevels of oil and enforcement of current laws that regulate suchdischarges are difficult. The development of on-shore facilities toprocess ballast water as a possible solution to the problem would bevery costly and of no helpwhen tankers take on or discharge ballast atsea to compensate for sea conditions. Moreover, eliminating oildischarge by providing tankers with tanks that carry only ballast wateris uneconomical because it reduces the oil-carrying capacity of thetanker.

The present invention discloses an on-board oilwater separation systemwhich provides a solution to the oil discharge problem. The system andthe novel vortex separator have a high separation effectiveness reducingoil content to below 20 parts per million. Further advantages of thepresent system are the high flowrate processing capacity, minimum spacerequire ments, minimum maintenance requirements, and low capital andoperation costs.

The heart of the present separation system is a vortex separator shownin FIGS. 1 and 2. The vortex separator 8 consists of a cylindricallateral wall section 10 which may be constructed from metal, fiberglass, plastic or any other rigid material. The cylindrical wall section10 is connected to end walls 12 and 14 generally formed from the samematerial as cylindrical wall 10. A plural ity of injectors 16 arelocated adjacent end wall 12 through which the oil-water mixture isinjected generally at a pressure above atmospheric into the separator ina tangential direction. The injectors 16 are located near to theperipheral wall 10 of the separator. The injectors may pass througheither the circumferential wall 10 or the end wall 12. Four injectorsare shown, but this number may be varied depending on the size of theseparator, the capacity of the pump, etc. The oil- Water mixture entersthe separator 8 at a very high flow rate so as to impart a strong swirlto the flow. As the mixture swirls axially, the difference incentrifugal forces due to the density differences between the water andthe oil accelerates the less dense oil radially inward to form a coreregion consisting almost entirely of oil.

The use of a confined vortex flow is very desirable for separating theoil from the water. The vortex flow has the unique property of providinglarge relative radial acceleration between twocomponents of differingspecific gravities. In the present application, the oil is concentratedat the center of the vortex where it can be conveniently removed througha small duct 18 located at the center of the end wall 14. All the wateris exhausted through a port 20 located at the center of the end wall 14,the duct 18 being concentric with the center of the water exhaust port20. The oil exhaust duct 18 may be flush with the end wall 14, may beretracted into the water exhaust duct 24 as shown in FIG. 3, butpreferably extends into the vortex chamber a distance of l or 2 percentof the length of the chamber. The end of the oil exhaust duct 18 may beslightly flared to provide a larger opening for the oil.

Positioned within the vortex chamber adjacent the end wall 14 are aplurality of injectors 22. Four injectors are shown, but any othernumber may be used. Clean water is injected into the chamber in atangential direction through the nozzles 22 in order to sustain thestrength of the vortex along the entire length of the separator, and toprevent the unseparated oil from entering the boundary layer on end wall14 and subsequently being exhausted with the water through the waterexhaust port 20.

An alternative embodiment is shown in FIG. 3 in which recirculated wateris fed into the injectors 22 rather than clean water. In FIG. 3, thewater outlet port 20 is connected to a duct 24, a portion of the waterbeing recirculated back into the separator through in jectors 22 bymeans of a pump 26, while the remainder of the water is removed from theseparator, and maybe dumped overboard depending on the application.

Tests were conducted on a vortex separator having an approximately threeto one Iength-to-diameter ratio. Equal flow rates of both the oil-watermixture injected through ducts l6 and clean water injected through ducts22 were used. The injection velocities were equal. Injected oil-watermixtures ranging from about 50 parts per million to about 7,500 partsper million were tested, and the water exhausted through port 20generally contained between five and fifteen parts per million of oil.Reducing the percentage of clean water injected into the chamber throughducts 22 relative to the percentage of oil-water mixture injected intothe chamber through injectors 16 resulted in the exhaust watercontaining a higher oil concentration than did the previous testsemploying equal percentages of clean water and the oil-water mixture.

Recirculation of the exhaust water into the injectors 22 as shown inFIG. 3 would increase the oil concentration in the exhaust water by somefactor less than two. Generally, recirculation of a part of the waterexhaust will not cause the exhaust water to exceed 20 parts per millionof oil.

The modified vortex oil-water separator shown in FIG. 3 contains abaffle 28 which is located halfway between the end walls 12 and 14.Other locations may be preferred for other embodiments. The baffle actsas a barrier between the oil-water mixture injected into the chamberthrough injectors l6, and the clean or recirculated water which isinjected into the chamber through injectors 22. The oil-water mixtureflows through an annulus concentric with the axis of the separator inthe baffle 28. In some applications the performance of the oil-waterseparator is improved with the baffle installed, particularly when theoil-water mixture contains small oil particles which result fromshearing of the oil-water mixture as the mixture is pumped or beinginjected. The use of the baffle prevents the mixing at large radii,where centrifugal forces are smallest, of the oil-water mixture and theclean or recirculated water.

The vortex separator'embodiment shown in FIG. 3 operates in a mannernearly identical to that of the separator shown in FIGS. 1 and. 2. Theoil-water mixture is injected tangentially at the end wall 12 throughinjectors 16. As the flow swirls toward baffle 28 and moves radiallyinward, centrifugal separation occurs. The flow approximates a freevortex where the tangential velocity is inversely proportional to theradius, except near the center where, due to viscous effects, itapproaches solid body rotation in which the tangential velocity isdirectly proportional to the radius. Thus, from the peripheral wall tothe viscous core, the radial acceleration field varies inverselywithradius cubed; inside the viscous region, it varies directly with radius.In this acceleration field, the oil droplets experience a radiallyinward force which increases with decreasing radius until the viscouscore is reached; the droplets are, therefore, differentially acceleratedwith respect to the water. Other key factors in determining thisdifferential acceleration are the specific gravity difference betweenthe oil and water, the tangential velocity of the flow at the peripheralwall 10 which is related to the jet injection velocity and the ratio ofinjection area to vortex chamber cross-sectional area, and thehydrodynamic drag on the droplets which is related to their velocity anddiameter.

Tests conducted on the embodiment of FIG. I show that the separationratio, the ratio of inlet mixture oil concentration, C to cleansed wateroil concentration, C increases with increasing inlet mixture oilconcentration. Separation ratios up to 780 have been obtained.

The teachings of the copending applications Ser. Nos. 125,154 and125,232 with regard to average residence time of the oil-water mixturein the separator, injection areas and secondary flow parameters aregenerally valid for the present embodiments.

FIG. 4 shows schematically a two-stage system which may form the basisof a shipboard oil-water separation system for cleaning ballast water orbilge water. At present there exists no known ballast water cleaningsystem having a high volume flow rate that will reduce the oilconcentration in the ballast water below parts per million. Most currentsystems use filtration techniques that have low processing rates, highmaintenance costs, and which may be adversely affected by normal pitchand roll of the ship. The systems are inadequate because impendingregulations will have very strict requirements upon discharging oilwater into the sea.

Referring specifically to FIG. 4, oily water is pumped from the ship'sballast tanks 40 through a pump 42 which is expected to be an existingpump on the ship and injected into the first stage separator 44. Vortexseparator 44 is preferably one of the separators shown 6 in FIGS. 1-3 ofthe present application, and preferably has a separation ratio of atleast 100. The oil port flow from separator 44 is placed in a slop tank46 on board the ship. A portion of the water port flow is recirculatedinto separator 44 by means of pump 48, and reinjected into the separator44 to maintain the strength of the vortex in separator 44 along thelength thereof and to prevent the unseparated oil from entering theboundary layer on the end wall of the vortex separator. The recirculatedflow may range between 25 percent to percent of the inlet flow forseparator 44 depending on the system performance required. The remainderof the first stage water port flow is pumped by means of pump 50 andinjected into the second stage separator 52. Separator 52 may beidentical to separator 44 except that the oil port flow from separator52 will contain approximately the same oil concentration as the ballastwater. Rather than diverting this flow to the slop tank 46, it iscombined with the ballast water fed into pump 42 by means of a mixingvalve 54. This recirculation of the oily water will reduce byapproximately one-half the slop tank storage requirements. As in thefirst stage separator, a portion of the water port flow of the secondstage separator 52 is reinjected into the separator 52 by means of pump56. If the oil concentration in the remaining water port flow issufficiently low, it is then piped overboard; otherwise, additionalseparator stages may be added until the desired purity is attained.

In many applications the water that is initially pumped from the ballasttanks is relatively clean. If during this portion of the processingcycle the oil concentrationin the water port flow of the first stage issufficiently clean to dump directly overboard, then succeeding separatorstages can be used in parallel to simultaneously process the relativelyoilfree water and thereby increase the processing rate. When the oilconcentration increases to a level where one stage processing isinadequate, the separators can be returned to operate in series.

FIG. 5 shows a variation of the ballast water cleaning system of FIG. 4.In the embodiment of FIG. 5, both relatively clean water andsubstantially pure oil result from the use of two different types ofseparators. The oily water from ballast tanks 40 is fed, as in FIG. 4,through a mixing valve 54 to a pump 42 and into a first stage separator44. A portion of the water port flow from separator 44 is recirculatedthrough pump 48. The remainder of the water port flow, if it issufficiently clean, is dumped overboard. If it is not sufficientlyclean, an additional separator stage may be required. The separator 44is similar to that described in FIGS. l-3 of the present application.

The oil port flow from separator 44, which generally will contain asubstantial amount of water, is fed to the input of a separator 60 whichis similar to that described in copending applications Ser. Nos. 125,154and 125,232. The separator 60 is of the type which producessubstantially pure oil at its outlet but a water port outflow which maycontain some oil. The oil port flow from separator 60 may be fed to sloptank 46 and, since relatively pure oil is obtained, the volume of tank46 may be reduced from the requirements of that needed in FIG. 4. Thewater port flow from separator 60, which contains some oil, isrecirculated into the first stage separator 44 by means of mixing valve54.

Separator 60 may use a core plate as described in the referencedcopending-applications, and the oil may be exhausted from one or bothends of the separator while the water is exhausted from the end wall ofthe separator opposite that from which the input oil-water mixture isinjected. No water recirculation is required with a separator 60 of thetype disclosed in the copending applications.

In some applications it may be necessary to use axialflow type pumps forthe embodiment of FIGS. 4 and 5 rather than the centrifugal pumpsnormally carried by ships. This is because of the small oil dropletsize, and the emulsification in the effluent from centrifugal pumps,which is largely determined by the shear and turbulence in the flow.However, both emulsified portions of the oil-water mixture, as well asthe unemulsified oil, can be removed from the pump effluent by theseparators disclosed herein. Emulsions cannot be broken, but as long astheir specific gravity is less than 1.0, they can be captured in thecore of oil produced in the separator.

it may also be desirable to use a radial diffuser to recover some of theenergy associated with swirl in the water exhaust from the separatorsdisclosed herein. It is desirable to have as much pressure recovery aspossible in order to reduce the pressure head required from the pumps. Adiffuser without flow separation and without excessively thick boundarylayers is preferred.

It may also be desirable to incorporate into the separator systems asensor control which monitors the oil concentration in the water exhaustfrom the final stage of the ballast water cleaning system. The sensorcontrol adjusts the inlet oil-water mixture flow rate, or may shut thesystem down if the oil concentration in the exhaust exceeds a presetamount. Such sensors and flow rate controls are disclosed'in thereferenced copending applications.

The disclosed ballast water separation system may be installed at anyconvenient place on a ship. Its preferred location will depend to alarge extent on whether or not the shipboard cargo and ballast pumps canbe used. The water exhaust from the separator is preferably dischargednear the ships water line, therefore, the separator should be as low inthe ship as possible to avoid unnecessary pump head rise.

While the present invention has been described in its preferredembodiments, it will be apparent to those skilled in the art thatchanges and modifications may be made to the construction andarrangement of parts without departing from the scope of the inventionas hereinafter claimed.

l claim:

1. A method for separating a mixture of oil and water into a componentconsisting primarily of oil and a component consisting of substantiallyoil-free water comprising the steps of injecting said mixturetangentially into a cylindrical chamber adjacent one end wall thereof tocause said mixture to swirl axially within said chamber and produce avortex, the oil being accelerated inwardly forming a core regionconsisting primarily of oil along the longitudinal axis of said chamber,said core region being surrounded by substantially oil-free water,removing the oil consisting of said core region from said chamberthrough a duct located in the center of the end wall of said chamberopposite the end of the chamber into which said mixture is injected,removing the substantially oil-free water surrounding said core regionfrom said chamber through a port located in the same end wall as saidduct, said port being concentric with surrounding said duct,

and injecting an additional volume of said substantially oil-free waterinto said chamber in a tangential direction through an injector locatedadjacent the end wall in which said port is located in order to sustainthe strength of the vortex along the longitudinal length of said chamberand to prevent unseparated oil contained in said mixture from flowingalong the end wall containing said port and subsequently being removedwith the water through said port.

2. The method of claim 1 wherein said step of injecting an additionalvolume of substantially oil-free water includes the step ofrecirculating at least a portion of the water which is removed from saidchamber through said port.

3. Apparatus for separating a mixture of oil and water into its separatecomponents comprising a chamber having a cylindrical lateral wallsection and first and second end walls,

first injecting means located adjacent said first end wall for injectingsaid mixture into said chamber in a tangential direction to cause saidmixture to swirl axially within said chamber and generate a vortextherein whereby a core consisting predominantly of oil is producedextending axially along the center of said chamber, the oil core beingsurrounded by water having a low oil content,

a duct for extracting the oil from said core located at the center ofsaid second end wall,

a port for extracting the water surrounding said core located in thesame end wall as said duct, said port being concentric with andsurrounding said duct,

and second injecting means located adjacent the said second end wall forinjecting into said chamber in a tangential direction an additionalvolume of substantially oil-free water from said port, said additionalwater sustaining the strength of the vortex in said chamber andpreventing unseparated oil contained in said mixture from flowing alongsaid second end wall and subsequently being removed with said waterthrough said port.

4. Apparatus as in claim 3 in which said duct projects a short distanceinto said chamber.

5. Apparatus as in claim 3 in which said first injecting means comprisesa plurality of injectors spaced about the circumference of said chamberfor injecting said mixture into said chamber in a tangential direction.

6. Apparatus as in claim 3 in which said second injecting meanscomprises a plurality of injectors spaced about the circumference ofsaid chamber for injecting said additional volume of higher densitymaterial into said chamber.

7. Apparatus as in claim 3 and including a second duct connected withsaid port for recirculating at least a portion of the water passingthrough said port to said second injecting means.

it 'b #4 i l

2. The method of claim 1 wherein said step of injecting an additionalvolume of substantially oil-free water includes the step ofrecirculating at least a portion of the water which is removed from saidchamber through said port.
 3. Apparatus for separating a mixture of oiland water into its separate components comprising a chamber having acylindrical lateral wall section and first and second end walls, firstinjecting means located adjacent said first end wall for injecting saidmixture into said chamber in a tangential direction to cause saidmixture to swirl axially within said chamber and generate a vortextherein whereby a core consisting predominantly of oil is producedextending axially along the center of said chamber, the oil core beingsurrounded by water having a low oil content, a duct for extracting theoil from said core located at the center of said second end wall, a portfor extracting the water surrounding said core located in the same endwall as said duct, said port being concentric with and surrounding saidduct, and second injecting means located adjacent the said second endwall for injecting into said chamber in a tangential direction anadditional volume of substantially oil-free water from said port, saidadditional water sustaining the strength of the vortex in said chamberand preventing unseparated oil contained in said mixture from flowingalong said second end wall and subsequently being removed with saidwater through said port.
 4. Apparatus as in claim 3 in which said ductprojects a short distance into said chamber.
 5. Apparatus as in claim 3in which said fIrst injecting means comprises a plurality of injectorsspaced about the circumference of said chamber for injecting saidmixture into said chamber in a tangential direction.
 6. Apparatus as inclaim 3 in which said second injecting means comprises a plurality ofinjectors spaced about the circumference of said chamber for injectingsaid additional volume of higher density material into said chamber. 7.Apparatus as in claim 3 and including a second duct connected with saidport for recirculating at least a portion of the water passing throughsaid port to said second injecting means.